1. Field of the Invention
The present invention relates to a display method and a display device for displaying letters, images, etc. as well as a displaying medium used therefor.
2. Description of the Prior Art
Recently, the need for displaying large capacity information including letters, images, etc. (hereinbelow called "image" all together) all at one time has increased with the development of the electronic file, etc. A display device is required which is capable of verifying an edited image or displaying design drawings at one time. The image may be edited e.g. by means and a word processor before outputting the image as a hard copy and the drawings may include graphics as a whole.
Heretofore a CRT, a liquid crystal display, etc. are devices used for such a display. However for the CRT it is not possible to extensively increase the size the image itself in view of the structure and the cost thereof. Since the resolving power of the CRT is restricted by the number of scanning lines, it is not possible to obtain a display having a satisfactorily high resolution. For this reason the CRT has a drawback that in the case where letters or images are fine, it is not possible to display them with a high quality. On the other hand, the liquid crystal display has an advantage that it is possible to reduce the thickness, the whole size and the weight with respect to the CRT. In contrast, it is difficult to fabricate a large enough liquid crystal display panel relative to the CRT with a high fabrication yield. Moreover, the resolving power of the liquid crystal display is not improved relative to the CRT.
On the other hand, a display device has been proposed, by which endless belt type photosensitive paper is used as a recording medium, on which a toner image is formed by using the electronic photographic process, and this recording medium is viewed by the eye through a glass plate while moving it through a display section. Since the recording medium has a belt shape, it is possible for this system to obtain a large size image in a simple manner only by enlarging the belt. Further, since it is so constructed that the image, which is to be displayed, is written-in by using light such as laser, etc. and visualized by using toner, it is possible to form easily a display image of high resolution. Therefore this system is expected as means capable of fulfilling the requirements described above.
However the display device of this system has following drawbacks. That is, since toner is used for forming images, a developing device for supplying toner to the recording medium and a mechanism for removing toner from the recording medium are necessary. Therefore the device has a problem that the size thereof is increased as the whole and the mechanism is complicated. Further, since the image display is repeatedly effected, toner images are successively formed and it is repeated to locate these toner images at the place opposite to the glass plate in the displaying section. For this reason it has a problem that toner scattered within the device in the course of use is attached on the inner surface of the glass plate, which is gradually coated with toner. Therefore, it is impossible to keep a good display state for a long period of time.